Enhanced power conversion efficiency of dye-sensitized solar cells with Li2SiO3-modified photoelectrode

Abstract

The effects of lithium silicate (LS) as a surface modifier on the performance of dye-sensitized solar cells (DSSCs) were studied. LS-modified TiO2 electrodes (LS-TiO2/FTO) prepared by a soaking process were applied to the photoelectrodes of DSSCs. The reference device without any modification showed performance of 0.68V of open-circuit voltage (Voc), 21.40mA/cm2 of short-circuit current (Jsc), and 63.21% of fill factor (FF), which led to a power conversion efficiency (PCE) of 9.20%, whereas for the device with the LS-TiO2/FTO electrode, the PCE was increased to 10.58% (Voc=0.79V, Jsc=20.22mA/cm2, and FF=66.21%). By monitoring the changes in dark current–voltage characteristics, normalized IPCE spectra, and electrochemical impedance spectra, it was revealed that the LS modification induced the formation of a surface dipole on the TiO2 photoelectrode, leading to the conduction band edge shift of TiO2 toward a negative direction, and thus to an enhancement in Voc and a decrease in Jsc.